1. Field of the Invention
The present invention relates to a method for producing an electrophotographic photosensitive member.
2. Description of the Related Art
As an electrophotographic photosensitive member to be mounted to an electrophotographic apparatus, an electrophotographic photosensitive member using organic photoconductive substances (organic charge generating substance and organic charge transporting substance) is used in many cases. In particular, an electrophotographic photosensitive member is often used, which has a laminated type photosensitive layer in which a charge generating layer containing a charge generating substance and a charge transporting layer containing a charge transporting substance are laminated in this order and the charge transporting layer is a surface layer.
As an electrophotographic apparatus repeatedly forms an image, an electrophotographic photosensitive member is demanded for having potential stability in order to provide a stable image quality even if being repeatedly used. In addition, when an electrophotographic photosensitive member is repeatedly used, the surface thereof is directly subjected to electrical external forces and mechanical external forces such as charging, exposing, developing, transferring and cleaning, and therefore an electrophotographic photosensitive member is also demanded for having durability (wear resistance) to such forces.
In regard to such a problem that an electrophotographic photosensitive member simultaneously satisfies wear resistance and potential stability, a method including allowing a charge transporting layer to have the concentration gradient of a charge transporting substance in the thickness direction thereof has been previously proposed. As the method including allowing a charge transporting layer to have the concentration gradient, Japanese Patent Application Laid-Open No. H05-66577 has proposed a method including laminating (applying many times) charge-transporting-layer coating liquids having a different charge transporting substance concentration. Japanese Patent Application Laid-Open No. 2006-138932 has proposed a method including laminating charge-transporting-layer coating liquids having a different charge transporting substance concentration and then annealing the resultant at a temperature near the glass transition temperature of a binder resin, or holding the resultant in a saturated vapor of a solvent.
However, in the method described in Japanese Patent Application Laid-Open No. H05-66577, since two charge transporting layers are required to be laminated, the number of steps increase as compared with the case where one charge transporting layer is provided, to thereby tend to increase the production cost. Furthermore, since the charge transporting substance is contained also in the vicinity of the surface of the charge transporting layer being an upper layer, wear resistance is not sufficiently achieved in some cases. In the method described in Japanese Patent Application Laid-Open No. 2006-138932, since a step of laminating charge transporting layers is required and an annealing step or a step of holding a coat in a solvent vapor is also added, the production process is complicated to thereby tend to increase the production cost.